3 research outputs found
Origami Multistabilty: From Single Vertices to Metasheets
We explore the surprisingly rich energy landscape of origami-like folding
planar structures. We show that the configuration space of rigid-paneled
degree-4 vertices, the simplest building blocks of such systems, consists of at
least two distinct branches meeting at the flat state. This suggests that
generic vertices are at least bistable, but we find that the nonlinear nature
of these branches allows for vertices with as many as five distinct stable
states. In vertices with collinear folds and/or symmetry, more branches emerge
leading to up to six stable states. Finally, we introduce a procedure to tile
arbitrary 4-vertices while preserving their stable states, thus allowing the
design and creation of multistable origami metasheets.Comment: For supplemental movies please visit
http://www.lorentz.leidenuniv.nl/~chen/multisheet
Experimental study of convection in the compressible regime
An experiment of thermal convection with significant compressible effects is
presented. The high-gravity environment of a centrifuge and the choice of xenon
gas enable us to observe an average adiabatic temperature gradient up to 3.5 K
cm over a 4 cm high cavity. At the highest rotation rate investigated,
9990 rpm, the superadiabatic temperature difference applied to the gas layer is
less than the adiabatic temperature difference. The convective regime is
characterized by a large Rayleigh number, about 10, and dominant
Coriolis forces (Ekman number of order 10). The analysis of temperature
and pressure fluctuations in our experiments shows that the dynamics of the
flow is in a quasi-geostrophic regime. Still, a classical power law (exponent
0.3 0.04) is observed between the Nusselt number (dimensionless heat
flux) and the superadiabatic Rayleigh number (dimensionless superadiabatic
temperature difference). However, a potential hysteresis is seen between this
classical high flux regime and a lower heat flux regime. It is unclear whether
this is due to compressible or Coriolis effects. In the transient regime of
convection from an isothermal state, we observe a local decrease of temperature
which can only be explained by adiabatic decompression